1. Field of the Invention
The invention relates to a method for the production of a composite glass sheet made up of at least two individual glass sheets and at least one thermoplastic film connecting the sheets together and with one or more metal wires, the metal wires being deposited and fixed in place on the intermediate layer and the film provided with the wires being joined to the individual glass sheets by the application of heat and pressure.
2. Discussion of the Related Art
Composite glass sheets with wires laid in the thermoplastic intermediate layer are employed in automobiles as electrically heated glass sheet and/or antenna sheets. Further applications of such glass are in the field of construction, in which they are employed, for instance, in heated glazing work, as alarm glazing for the protection of rooms against breaking in or breaking out and for glass screens to prevent the passage of electromagnetic radiation or for decorative purposes.
If the metal wires serve as heating wires, a series of heating wires are generally connected in a parallel circuit with bus conductors arranged along two opposite edges of the glass sheet.
For the deposition and fixing in place of the wires on the thermoplastic film, various methods have been developed. In the case of a parallel arrangement of the wires, the buses are made in the form of thin tapes or ribbons and are fixed in position on the thermoplastic film, which has been cut to the final size. Then in the method which is most frequently employed in practice the wires are spanned out over the thermoplastic film cut to its final size and fixed in place by the application of heat and pressure. After this the wire ends projecting past the film edges are cut off so as to be made flush with the film.
In the case of composite glass sheeting, in which the metal wires are applied in this manner, the embedded wires extend out past the buses as far as the peripheral surface of the composite glass sheet. Because of the fact that after the bonding process there is not always a firm, adhesive connection between the surface of the wires and the material of the thermoplastic film, it is possible for small channels to be produced along the wire ends, which are open towards the peripheral surface. Then in the course of time moisture is able to diffuse inwards, and it may for example cause corrosion on the bus and at the points of contact between the wires and the buses.